Access to the bloodstream of a patient receiving intermittent dialysis for a chronic renal failure is necessary throughout the dialysis which may require from two to six hours. Earliest access employed cannulas, that is, hollow glass or metal tubes inserted into an artery and a vein. Repeat need for access brought about a substitution of plastic for the glass or metal cannula and during the 1950's, the external ends of the plastic cannulas were connected with a short length of plastic tubing thereby short circuiting the arterial blood into the vein; this provided an external, available access to the blood stream for repeated dialyses without the necessity for needle penetration of the artery and vein for each dialysis. Such external arteriovenous shunts are currently in use on a portion of those patients receiving intermittent hemodialysis with artificial kidneys. Connection to the artificial kidney is made by attaching blood tubing from the artificial kidney to the external connectors on each of the two portions of the external plastic tubes forming the arteriovenous shunt.
By 1960, problems with the blood flowing in the external plastic tubes of the shunt during the time between dialyses, such as clotting, infection and inadvertent separation of the external tube connector, led to an alternative shunt system. In this system, an artery is shunted to a vein entirely under the skin and the shunt is left in place indefinitely. Resultant enlarged veins provide access sites for penetration with a fistula. Fistulas, each consisting of a needle attached to a short section of blood tubing terminating at its outer end in a connector, are then attached to blood tubes associated with the artificial kidney. Access to the bloodstream by fistula is currently used to a greater extent in artificial kidney dialysis than external arteriovenous shunts.
One problem is ever present in delivering blood from the patient to an artificial kidney irrespective of whether the blood access is by fistula or from an external arteriovenous shunt. That problem is inadvertent separation of the members linking the blood tubes to the blood access source. Typically, the connector consists of a short length of Teflon tubing, having its outer surface etched and its ends smooth and slightly beveled for snug fit into a tapered bore of the connector body on the fistula or external shunt, and a similar bore available on the blood tube. After the connection is made by firmly pressing the connector parts together, and overlying tape is applied, the joint is nevertheless subject to forceful disconnection at any time during the two to six-hour period the dialysis is in progress. Although accidental disconnection occurs only during a small fraction of the time, it is traumatic when it does occur and can cause death unless immediate corrective steps are taken to stop the loss of blood.
The improved connector of this invention provides a locking connection that prevents accidental disengagement of the blood tube from the blood access fistula or external shunt and concurrently provides an available alternative tapered connector of the type heretofore used. No connector providing such alternative connections has been available heretofore to the best of applicant's knowledge.